KR20200136406A - Display panel, display device, and method of sorting retardation layer of display panel - Google Patents

Abstract

A display panel capable of suppressing deterioration of color sense is provided regardless of the reflectance of the display element. It has a display element (A), a retardation layer (B) disposed on the light emission surface side of the display element, and a polarizer (C) disposed on the light emission surface side of the retardation layer, and the retardation layer (B) is λ/ A display panel having 4 retardation layers (B1), and wherein the in-plane retardation of the λ/4 retardation layer (B1) satisfies Condition 1 below.
<Condition 1>
The spectral reflectance of the display element is measured by the SCI method, and the average of the reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/4 retardation layer is -4.6002x+119.24 nm or more and -4.6002x+129.24 nm or less.

Description

Display panel, display device, and method of sorting retardation layer of display panel

The present invention relates to a display panel, a display device, and a method for sorting a retardation layer of a display panel.

Electroluminescent display elements (hereinafter, sometimes abbreviated as'EL elements') have a wide field of view due to self-luminescence, and have low power consumption compared to plasma light-emitting elements, and thus their application to image display devices has become practical. Has become. In particular, since an organic EL device using an organic compound as a light emitting material can significantly reduce the applied voltage compared to an inorganic EL device using an inorganic compound, its use as a display device has been studied in various ways.

An organic EL device is generally known to have a structure in which a first electrode, a light emitting layer, and a second electrode are sequentially stacked on a transparent substrate, and a transparent electrode is used as the first electrode, and a metal electrode is used as the second electrode. Then, a bottom emission type in which light emission from the light-emitting layer is extracted from the transparent substrate side, a metal electrode is used as the first electrode, a transparent electrode is used as the second electrode, and light emission from the light-emitting layer is extracted from the second electrode side. There is one of the top emission type (for example, Patent Documents 1 and 2).

In order to efficiently utilize the light of the light emitting layer in any form of the organic EL element, the metal electrode is often used having excellent reflectivity. On the other hand, in the organic EL device using such a metal electrode, reflection of external light is large, and the contrast sometimes decreases. In addition, in display devices other than a display device including an organic EL device (for example, a display device including a micro LED device, a display device in which a resistive touch panel is disposed on the display device), the contrast due to reflection of external light The decline in the future is a problem.

Methods of suppressing reflection of external light in a display device have been studied in various ways. As one of such a method, it is known to use a so-called circularly polarizing plate formed by laminating a retardation plate and a polarizing plate (for example, Patent Document 3).

Japanese Patent Publication No. 2007-294421 Japanese Patent Publication No. 2007-80604 Japanese Patent Publication No. 2015-57666

However, when the circularly polarizing plate as in Patent Document 3 is incorporated in a display device having a large reflection of external light, it has been seen here and there that the color sense of the display device is damaged.

As a result of intensive research, the present inventors found that a display device having large reflection of external light has a difference in spectral distribution of reflected light due to a difference in the configuration of the display element (for example, a difference in the metal composition of the metal electrode constituting the display element). I found out the facts. Further, the inventors of the present invention found that by combining an appropriate retardation layer according to the spectrum distribution of the reflected light of the display element, it was possible to suppress a decrease in color sensation of the display panel and the display device. Arrived.

That is, the present invention provides the following [1] to [3].

[1] having a display element (A), a retardation layer (B) disposed on the light exit surface side of the display element, and a polarizer (C) disposed on the light emission surface side of the retardation layer, and the retardation layer (B) Has a λ/4 retardation layer (B1), and the in-plane retardation of the λ/4 phase difference layer (B1) satisfies Condition 1 below.

<Condition 1>

The spectral reflectance of the display element is measured by the SCI method, and the average of the reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/4 retardation layer is -4.6002x+119.24 nm or more and -4.6002x+129.24 nm or less.

[2] A display device comprising the display panel according to [1].

[3] comprising a display element (A), a retardation layer (B) disposed on the light exit surface side of the display element, and a polarizer (C) disposed on the light emission surface side of the retardation layer, and the retardation layer (B) In the display panel having a λ/4 phase difference layer (B1), as the λ/4 phase difference layer (B1), a λ/4 phase difference layer that satisfies the following condition 1 is selected, and the phase difference layer of the display panel is selected. Way.

<Condition 1>

The spectral reflectance of the display element is measured by the SCI method, and the average of the reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/4 retardation layer is -4.6002x+119.24 nm or more and -4.6002x+129.24 nm or less.

In the display panel and display device of the present invention, it is possible to suppress a decrease in color sense of the display panel and display device due to reflection of external light. Further, in the method of sorting the retardation layer of a display panel according to the present invention, the retardation layer in which the color sense of the display panel is deteriorated can be appropriately selected, and thus product design of the display panel can be improved.

1 is a cross-sectional view showing an embodiment of a display panel according to the present invention.
2 is a cross-sectional view showing another embodiment of the display panel of the present invention.
3 is a cross-sectional view showing an embodiment of a laminate having a retardation layer disposed on a display panel of the present invention.
4 is a cross-sectional view showing another embodiment of a laminate having a retardation layer disposed on a display panel of the present invention.
5 is a diagram showing spectral reflectance of commercially available organic EL display elements A to C.
6 is a diagram showing a relationship between a saturation (y-axis) based on reflected light of a display panel in which a retardation layer and a polarizer are stacked on commercially available organic EL display devices A to C, and an in-plane retardation (x-axis) of the retardation layer .
7 is a diagram showing an approximate straight line serving as a criterion for condition 1;
8 is a diagram showing an approximate straight line serving as a criterion for condition 2;

Hereinafter, an embodiment of the present invention will be described.

[Display Panel]

The display panel of the present invention has a display element (A), a retardation layer (B) disposed on the light emission surface side of the display element, and a polarizer (C) disposed on the light emission surface side of the retardation layer, and the phase difference The layer (B) has a λ/4 phase difference layer (B1), and the in-plane retardation of the λ/4 phase difference layer (B1) satisfies the condition 1 below.

<Condition 1>

The spectral reflectance of the display element is measured by the SCI method, and the average of the reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/4 retardation layer is -4.6002x+119.24 nm or more and -4.6002x+129.24 nm or less.

<<condition 1>>

In the display panel of the present invention, the spectral reflectance of the display element is measured by the SCI method, the average of the reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/4 retardation layer is -4.6002x+119.24nm or more and -4.6002x+129.24nm or less.

Hereinafter, the technical idea of condition 1 will be described.

5 is a diagram showing a result of measuring the spectral reflectances of organic EL elements A to C included in three different types of organic EL display panels on the market by the SCI method. From Fig. 5, it can be seen that the reflectance of the organic EL element for each wavelength is different depending on the model. In addition, from FIG. 5, it can be understood that the difference in reflectance for each wavelength of the display element may affect the color sense of the display panel or the display device.

Regarding the organic EL elements A to C of Fig. 5, R ₁ /R ₂ is calculated by taking the average of reflectances of 400 nm or more and less than 550 nm as R ₁ , and the average of reflectances of 550 nm or more and less than 700 nm as R ₂ , The organic EL element A is 1.28, the organic EL element B is 1.04, and the organic EL element C is 0.78.

The human eye has high sensitivity around 550 nm wavelength. Therefore, it can be said that R ₁ /R ₂ indicates whether the spectral spectrum of light reflected from the display element is biased to either the blue side or the red side, with a boundary of 550 nm having high sensitivity to the human eye.

6 shows the spectral reflectances of organic EL display panels A to C formed by arranging a λ/4 retardation layer, a λ/2 phase difference layer, and a polarizer in this order on the organic EL elements A to C of FIG. 5 in the SCI method. It is a diagram in which the x-axis is the in-plane phase difference of the λ/4 phase difference layer and the y-axis is the saturation when measuring and calculating "saturation" from the measured reflected light. In addition, although not shown, the in-plane retardation of the λ/2 phase difference layer used in the measurement of FIG. 6 is twice the in-plane phase difference of the λ/4 phase difference layer. In addition, in the measurement of FIG. 6, the angle formed by the absorption axis of the polarizer and the alignment axis of the λ/4 phase difference layer is +75°, and the angle formed by the absorption axis of the polarizer and the alignment axis of the λ/2 phase difference layer is +15°. Has been. In addition, the graph of Fig. 6 is smoothed by Microsoft Excel (registered trademark) 2013.

In addition, saturation is a value obtained from the following formula based on a ^* and b ^* of the Lab color system.

Saturation=[(a ^* ) ² +(b ^* ) ² ] ^1/2

From Fig. 6, the in-plane retardation of the λ/4 retardation layer when the saturation becomes the minimum value is read as 118.35 nm for the organic EL display panel A, 119.45 nm for the organic EL display panel B, and 120.65 nm for the organic EL display panel C. I can.

In addition, although not shown, the in-plane retardation of the λ/2 retardation layer when the saturation reaches the minimum value is 236.7 nm for the organic EL display panel A, 238.9 nm for the organic EL display panel B, and 241.3 nm for the organic EL display panel C. Can be read as. Fig. 7 shows an approximate straight line by the least squares method added to a scatter plot in which the in-plane retardation of the λ/4 phase difference layer is the y-axis when the saturation read from Fig. 6 is the minimum value and R ₁ /R ₂ is the x-axis. It is a drawing.

In addition, Fig. 8 is a diagram in which an approximate straight line by the least squares method is added to a scatter plot in which R ₁ /R ₂ is the x-axis and the in-plane retardation of the λ/2 phase difference layer is the y-axis when the saturation becomes the minimum value. .

From FIGS. 7 and 8, it can be seen that R ₁ /R ₂ and the in-plane retardation of the λ/4 retardation layer and the λ/2 retardation layer representing the minimum saturation value of the display panel have a proportional relationship. In other words, when the value of R ₁ /R ₂ of the display element is obtained, based on the approximate straight lines of Figs. 7 and 8, the saturation of the reflected light of the display panel is lowered to suppress the color sensation, so the appropriate λ/4 retardation layer and λ /2 The in-plane retardation of the retardation layer can be known.

In condition 1, the in-plane retardation calculated from the approximate straight line in Fig. 7 is given the in-plane retardation and the position of the optimal λ/4 retardation layer capable of suppressing the color sense of reflected light, and ±5 nm around the optimal value. The range is defined as the allowable range.

When condition 1 is not satisfied (when the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/4 retardation layer is less than -4.6002x+119.24nm, or more than -4.6002x+129.24nm) , The color of the reflected light from the display panel cannot be suppressed.

In condition 1, the in-plane retardation of the λ/4 phase difference layer is preferably -4.6002x+121.24 nm or more -4.6002x+127.24 nm or less, and more preferably -4.6002x+123.24 nm or more -4.6002x+125.24 nm or less. Do.

Incidentally, in this specification, the in-plane retardation under Condition 1 and Condition 2 to be described later refers to the in-plane retardation at a wavelength of 550 nm. In addition, the in-plane retardation is the refractive index n _x in the slow axis direction, which is the direction in which the refractive index is the largest in the plane of the retardation layer, and the refractive index n _y in the fast axis direction, which is orthogonal to the slow axis direction in the plane of the retardation layer. , By the thickness d (nm) of the retardation layer, expressed by the following formula.

In-plane retardation (Re)=(n _x -n _y )×d

Further, in the display panel of the present invention, it is preferable that the retardation layer (B) has a λ/2 retardation layer (B2).

Since the retardation layer (B) has a lambda /2 retardation layer (B2) in addition to the lambda /4 retardation layer (B1), it is possible to easily suppress reflection of the display panel in a wide wavelength range.

In addition, in the display panel of the present invention, it is preferable that the in-plane retardation of the λ/2 retardation layer (B2) satisfies Condition 2 below.

<Condition 2>

The spectral reflectance of the display element is measured by the SCI method, and the average of reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/2 phase difference layer is -9.2004x+238.47nm or more and -9.2004x+258.47nm or less.

In condition 2, the in-plane retardation calculated from the approximate straight line in FIG. 8 is given the in-plane retardation and position of the optimal λ/2 retardation layer capable of suppressing the color sense of the reflected light, and ±10 nm around the optimum value. The range is defined as the allowable range. By satisfying the condition 2, the color of the reflected light of the display panel can be further suppressed.

In condition 2, the in-plane retardation of the λ/2 retardation layer is preferably -9.2004x+242.47nm or more -9.2004x+254.47nm or less, and more preferably -9.2004x+246.47nm or more -9.2004x+250.47nm or less. Do.

In the present specification, the reflectance of the SCI method means total light reflectance. SCI is a reflectance calculated from the measured value by applying light to the sample surface from all directions using an integrating sphere, closing the light trap, measuring all reflected light including the specular reflection direction. A typical SCI measuring device has a configuration conforming to the geometric condition c of JIS Z8722:2009. More specifically, in typical SCI and SCE measuring devices, the position of the light receiver is +8 degrees with respect to the normal line of the sample, the aperture angle of the light receiver is 10 degrees, and the position of the light trap is- It is 8 degrees, and the cover range of the light trap is 10 degrees. As such a measuring device, the brand name CM-2002 manufactured by Konica Minolta Corporation is mentioned.

It is preferable to measure the spectral reflectance of the SCI method every 1 nm, but when the measurement wavelength interval of the measuring device exceeds 1 nm, the absolute value of the change in reflectance for each 1 nm within the measurement interval is considered to be equal, It is preferable to calculate R ₁ /R ₂ .

In addition, in this specification, the spectral reflectance and R ₁ /R ₂ of a display element, and saturation of a display panel mean the average value of 16 measured values. In the 16 measurement points, the area of 1 cm from the outer edge of the measurement sample is used as a margin, and 16 points of intersection are measured when a line dividing the vertical direction and the horizontal direction into 5 equal parts is drawn about the area inside the margin. It is preferable to make it the center of. When the measurement sample is a square, the area of 1 cm from the outer edge of the rectangle is used as a blank, and the area inside the blank is measured centering on 16 points of intersections of lines divided into 5 equal parts in the vertical and horizontal directions. It is preferable to calculate the average value. In addition, when the measurement sample has a shape other than a square such as a circle, an oval, a triangle, a pentagon, etc., it is preferable to draw a square with the largest area inscribed to these shapes, and perform 16 measurements with respect to the square by the above method. Do.

1 and 2 are cross-sectional views showing an embodiment of a display panel 100 of the present invention.

1 and 2, the display panel 100 of the present invention includes a display element (A) 10, a retardation layer (B) 20 disposed on the light exit surface side of the display element, and , It has a polarizer (C) 30 which is arrange|positioned on the light exit surface side of the retardation layer (B) 20.

In addition, the display panel 100 of FIGS. 1 and 2 has a λ/4 retardation layer 20a as the retardation layer 20, and the display panel 100 of FIG. 2 is a retardation layer 20. , λ/2 phase difference layer 20b is further provided.

<Display element (A)>

As a display element, an organic EL element, an inorganic EL element, a micro LED element, a liquid crystal element, a plasma element, etc. are mentioned. Further, the liquid crystal display element may be an in-cell touch panel liquid crystal display element having a touch panel function in the element.

Among these display elements, the organic EL element and the micro LED element are effective in that their reflectance is high, and the problem of color sensation caused by reflection of external light is liable to occur, and thus the effect of the present invention is easily exhibited.

In the display element, when the reflectance of a wavelength of 400 nm or more and 700 nm or less is measured by the SCI method, the average reflectance of each wavelength is preferably 35% or more, and more preferably 40% or more. The display element having such a high reflectance is effective in that the effect of the present invention is easily exhibited because the problem of color sensation caused by reflection of external light is likely to occur.

<Phase difference layer (B)>

The retardation layer (B) has at least a λ/4 retardation layer (B1). In addition, it is preferable that the retardation layer (B) further includes a λ/2 retardation layer (B1).

The λ/4 retardation layer (B1) and the λ/2 retardation layer (B2) are not particularly limited to the material constituting the retardation layer, and may be a retardation layer formed of a composition containing a liquid crystal compound or a retardation layer obtained by stretching a polymer film. , You may have both layers.

A retardation layer formed of a composition containing a liquid crystal compound is usually formed by applying a composition for forming a retardation layer on a transparent substrate, drying it, and curing if necessary. In addition, as shown in Figs. 3 and 4, it is preferable to have an alignment film 22 on the surface of the transparent substrate 21 on the side where the retardation layer 20 is formed.

The λ/4 retardation layer (B1) is not particularly limited as long as it satisfies the condition 1, but from the viewpoint of versatility, it is preferable as long as it has positive dispersion.

The positive dispersion is a characteristic in which the in-plane retardation imparted to the transmitted light decreases as the wavelength increases. Specifically, the in-plane retardation (Re450) at a wavelength of 450 nm and the in-plane phase difference (Re550) at a wavelength of 550 nm The relationship is a characteristic of Re450> Re550. On the other hand, inverse dispersion is a characteristic of Re450<Re550.

The in-plane retardation (Re550) of the λ/4 retardation layer is preferably 105 to 135 nm, more preferably 110 to 130 nm, and even more preferably 113 to 127 nm.

In this specification, the in-plane retardation (in-plane retardation, Re) and the retardation in the thickness direction (thickness direction retardation, Rth) are the refractive index in the slow axis direction in the plane nx, and the direction orthogonal to nx in the plane. When the refractive index of ny, nx, and ny in the direction orthogonal to ny, nx, and ny are nz, and the film thickness is d (nm), it can be expressed by the following equation.

In-plane retardation (Re) = (nx-ny) × d

The retardation in the thickness direction (Rth)=((nx+ny)/2-nz)×d

In addition, the λ/4 retardation layer preferably has Re450/Re550 of 1.13 or less, more preferably 1.10 or less, and even more preferably 1.07 or less. By setting Re450/Re550 of the λ/4 phase difference layer to 1.13 or less, it is possible to more easily suppress a decrease in color sensation. The lower limit of Re450/Re550 of the λ/4 retardation layer is not particularly limited, but is usually 1.04 or more.

When only the λ/4 retardation layer (B1) is used as the retardation layer (B), the angle between the orientation axis of the λ/4 retardation layer and the absorption axis of the polarizer is preferably 45±5°, and 45± It is more preferable to set it as 2 degrees.

The λ/2 retardation layer (B2) is not particularly limited, but from the viewpoint of versatility, it is preferable as long as it has positive dispersion.

The in-plane retardation (Re550) of the λ/2 retardation layer is preferably 210 to 270 nm, more preferably 220 to 260 nm, and still more preferably 225 to 255 nm.

In addition, in the λ/2 retardation layer, Re450/Re550 is preferably 1.13 or less, more preferably 1.10 or less, and still more preferably 1.07 or less. By setting Re450/Re550 of the λ/2 phase difference layer to 1.13 or less, it is possible to more easily suppress a decrease in color sensation. The lower limit of Re450/Re550 of the λ/2 retardation layer is not particularly limited, but is usually 1.04 or more.

When a λ/4 phase difference layer (B1) and a λ/2 phase difference layer (B2) are used as the phase difference layer (B), the angle formed by the orientation axis of each phase difference layer and the absorption axis of the polarizer is as follows (i) Or the range of (ii) is preferable.

(I) As a first example, the angle between the slow axis of the λ/2 retardation layer and the absorption axis of the polarizer layer is preferably 15±8°, and more preferably 15±6°. In this case, the angle between the slow axis of the λ/4 phase difference layer and the absorption axis of the polarizer layer is preferably 75±15°, and more preferably 75±13°.

(Ii) As a second example, the angle between the slow axis of the λ/2 phase difference layer and the absorption axis of the polarizer layer is preferably 75±15°, and more preferably 75±13°. In this case, the angle between the slow axis of the λ/4 phase difference layer and the absorption axis of the polarizer layer is preferably 15±8°, and more preferably 15±6°.

<<Liquid Crystalline Compound>>

There is no particular limitation on the kind of the liquid crystal compound used for forming the retardation layer. For example, after forming a low-molecular liquid crystal compound in nematic alignment in a liquid crystal state, after forming a retardation layer obtained by immobilizing by photo-crosslinking or thermal crosslinking, or a polymeric liquid crystal compound in a nematic alignment in a liquid crystal state, You may use a retardation layer obtained by fixing the orientation by cooling. In the present invention, even when a liquid crystal compound is used for the retardation layer, the retardation layer is a layer formed by fixing the liquid crystal compound by polymerization or the like, and after becoming a layer, it is not necessary to show liquid crystal properties any more. The polymerizable liquid crystal compound may be a polyfunctional polymerizable liquid crystal compound or a monofunctional polymerizable liquid crystal compound. In addition, the liquid crystal compound may be a discotic liquid crystal compound or a rod-shaped liquid crystal compound.

In the phase difference layer, it is preferable that the liquid crystal compound is fixed in any alignment state of vertical mixing, horizontal alignment, hybrid alignment, and oblique alignment. From the viewpoint that the viewing angle dependence can be made symmetric, the disk surface of the discotic liquid crystal compound is substantially perpendicular to the film surface (phase difference layer surface), or the long axis of the rod-shaped liquid crystal compound is relative to the film surface (phase difference layer surface). It is preferred that it is substantially horizontal.

When the discotic liquid crystal compound is substantially perpendicular, it means that the average value of the angle between the film surface (phase difference layer surface) and the disk surface of the discotic liquid crystal compound is in the range of 70° to 90°. It is preferably in the range of 80° to 90°, more preferably 85° to 90°.

When the rod-shaped liquid crystal compound is substantially horizontal, it means that the angle between the film surface (phase difference surface) and the director of the rod-shaped liquid crystal compound is in the range of 0° to 20°. It is preferably 0° to 10°, more preferably 0° to 5°.

The retardation layer containing the liquid crystal compound may consist of only one layer, or may be a laminate of two or more layers.

The retardation layer containing a liquid crystal compound comprises a liquid crystal compound such as a rod-shaped liquid crystal compound or a discotic liquid crystal compound, and a coating liquid containing a polymerization initiator, alignment control agent, or other additive described later as required, as a transparent substrate. It can be formed by applying on it. It is preferable to form a retardation layer by forming an alignment film on a transparent substrate and applying a coating liquid to the surface of the alignment film. The thickness of the retardation layer is preferably 10 µm or less, more preferably 7 µm or less, and still more preferably 5 µm or less. The lower limit of the thickness of the retardation layer is not particularly limited, but is usually about 0.1 μm.

-Discotic liquid crystal compound-

In the present invention, it is preferable to use a discotic liquid crystal compound for formation of a retardation layer. Discotic liquid crystal compounds are described in various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., vol. 71, page 111 (1981); Japanese Chemical Society, Quarterly Chemistry Review, No. 22, liquid crystal liquid crystal) Of Chemistry, Chapter 5, Chapter 10, Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., page 1794 (1985); J. Zhang et al., J. Am. Chem. Soc., vol. 116, page 2655 (1994) et al.). The polymerization of discotic liquid crystal compounds is described in Japanese Patent Laid-Open No. 8-27284.

It is preferable that the discotic liquid crystal compound has a polymerizable group so that it can be fixed by polymerization. For example, a structure in which a polymerizable group is bonded as a substituent to a disk-shaped core of a discotic liquid crystal compound is conceivable, but when a polymerizable group is directly connected to the disk-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a structure having a linking group between the disk-shaped core and the polymerizable group is preferable. That is, it is preferable that the discotic liquid crystal compound having a polymerizable group is a compound represented by the following formula.

In the formula, D is a disk-shaped core, L is a divalent linking group, P is a polymerizable group, and n is an integer of 1 to 12. Preferred specific examples of the disk-shaped core (D), the divalent linking group (L), and the polymerizable group (P) in the formula are, respectively, (D1) to (D15) and (L1) described in Japanese Patent Laid-Open No. 2001-4837. ) To (L25), (P1) to (P18), and the contents described in the same publication can be preferably used. Further, the discotic nematic liquid crystal phase-solid phase transition temperature of the liquid crystal compound is preferably 30 to 300°C, and more preferably 30 to 170°C.

-Bar-type liquid crystal compound-

As the liquid crystal compound for forming the retardation layer, a rod-shaped liquid crystal compound may be used. As a rod-shaped liquid crystal compound, azomethines, azoxyls, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrims Midines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolans, and alkenylcyclohexylbenzonitriles are preferably exemplified. In addition to the low-molecular liquid crystal compounds as described above, a high-molecular liquid crystal compound can also be used. It is more preferable to fix the orientation of the rod-like liquid crystal compound by polymerization. The liquid crystal compound preferably has a partial structure capable of causing polymerization or crosslinking reaction by actinic light, electron beam, heat, or the like, and more preferably one having a polymerizable group.

The number of partial structures is preferably 1 to 6, and more preferably 1 to 3. As a polymerizable rod-shaped liquid crystal compound, Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials, Vol. 5, p. 107 (1993), U.S. Patent No.83327, 5622648, 5770107, International Publication WO95/22586 , No. 95/24455, No. 97/00600, No. 98/23580, No. 98/52905, Japanese Patent Laid-Open No. 1-272551, No. 6-16616, No. 7-110469 The compounds described in JP Publication No. 11-80081, JP 2001-328973 A, and the like can be used.

As a specific example of a rod-shaped liquid crystal compound, the compound represented by following formula (1)-(17) is mentioned.

In addition, as a liquid crystal compound showing reverse dispersibility, Japanese Patent Publication No. 2010-537954, Japanese Patent Publication No. 2010-537955, Japanese Patent Publication No. 2010-522892, and Japanese Patent Publication No. 2010-522893 , And Japanese Patent Publication No. 2013-509458, etc., and Japanese Patent No. 5892158, Japanese Patent No. 579136, Japanese Patent No. 594777, and Japanese Patent No. 6015655. The compound which has become exemplified.

The liquid crystal compounds can be used alone or in combination of two or more. In the case of one type alone, it is preferable that the one type of liquid crystal compound is a polymerizable liquid crystal compound. Moreover, when using in combination of 2 or more types, it is preferable that at least 1 type is a polymeric liquid crystal compound, and it is more preferable that all are polymeric liquid crystal compounds.

<<polymerization initiator>>

The oriented liquid crystal compound is fixed by maintaining the oriented state. It is preferable to use a polymerization reaction for fixing, and the polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photo polymerization reaction using a photopolymerization initiator. Among these, a photopolymerization reaction is preferable. Examples of the photopolymerization initiator include α-carbonyl compounds (refer to the respective specifications of U.S. Patent No.2367661 and 2367670), an acyloin ether (refer to the specification of U.S. Patent No. 2448828), and an α-hydrocarbon substituted aromatic acyloin compound ( U.S. Patent No. 2722512), polynuclear quinone compounds (see U.S. Patent No. 3046127, 2951758), a combination of a triaryl imadazol dimer and p-aminophenyl ketone (see U.S. Patent No. 3549367) , Acridine and phenazine compounds (see Japanese Patent Laid-Open Publication No. 60-105667, US Patent No. 4239850), and oxadiazole compounds (see US Patent No. 4212970).

The amount of the polymerization initiator to be used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the total solid content of the composition for forming a retardation layer. It is preferable to use ultraviolet rays for light irradiation for polymerization of the liquid crystal compound. The irradiation energy is preferably 20 mJ/cm 2 to 50 J/cm 2, more preferably 100 to 800 mJ/cm 2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

<<surfactant>>

It is preferable that the composition for forming a retardation layer contains a surfactant. In addition, among surfactants, it is preferable to select and use at least one selected from a fluorine-based surfactant having a polymerizable group and a silicone-based surfactant having a polymerizable group.

The content of the surfactant is preferably 0.01 to 2.0% by mass and more preferably 0.1 to 1.0% by mass with respect to the total solid content of the composition for forming a retardation layer.

<< solvent >>

The composition for forming a retardation layer usually contains a solvent.

As a solvent, ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, N-methyl-2-pyrrolidone, etc.), ethers (dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons Compounds (hexane, etc.), alicyclic hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), halogenated carbons (dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.) ), alcohols (butanol, cyclohexanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), cellosolve acetates, sulfoxides (dimethyl sulfoxide, etc.), amides (dimethylformamide , Dimethylacetamide, etc.) etc. can be illustrated, and a mixture thereof may be sufficient.

<<Other additives>>

In the present invention, the composition for forming a retardation layer may have a plasticizer, a polymerizable monomer, and the like in addition to the above components. It is preferable that these components have compatibility with a liquid crystalline compound and do not inhibit orientation.

Examples of the polymerizable monomer include radical polymerizable or cationic polymerizable compounds, preferably polyfunctional radical polymerizable monomers, and copolymerizable compounds with the aforementioned polymerizable group-containing liquid crystal compounds. For example, the compounds described in paragraphs 0018 to 0020 of Japanese Unexamined Patent Application Publication No. 2002-296423 can be mentioned. The addition amount of the polymerizable compound is preferably 1 to 50 parts by mass, more preferably 5 to 30 parts by mass, based on 100 parts by mass of the liquid crystal compound.

<<Phase difference layer application method>>

The application of the composition for forming a retardation layer can be performed by a known method (eg, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method).

<<Transparent Equipment>>

The transparent base material functions as a support for the retardation layer or has a role of protecting the retardation layer.

It is preferable that the transparent substrate is optically isotropic. The transparent substrate may be formed of a polymer or may be formed of glass.

Examples of the polymer include cellulose acylate, polycarbonate polymer, polyester polymer such as polyethylene terephthalate and polyethylene naphthalate, acrylic polymer such as polymethyl methacrylate, polystyrene or acrylonitrile/styrene copolymer (AS resin ) And the like can be used. In addition, polyolefins such as polyethylene and polypropylene, polyolefin polymers such as ethylene/propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamides, imide polymers, sulfone polymers, and polyethersulfone polymers , Polyetheretherketone polymer, polyphenylene sulfide polymer, vinylidene chloride polymer, vinyl alcohol polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or these polymers Mixture, etc. are mentioned.

The thickness of the transparent substrate is usually about 25 to 125 μm in the case of a transparent substrate formed of a polymer, and is usually about 100 μm to 5 mm in the case of a transparent substrate formed of glass.

<Orientation membrane>

The alignment film has a role of facilitating alignment of a compound (eg, a liquid crystal compound) contained in the retardation layer when forming a retardation layer by applying, drying, and curing the retardation layer forming composition.

Further, even if an alignment film is provided at the time of formation of the retardation layer, if the retardation layer is transferred to another member and the alignment film is not transferred during transfer, a display panel having no alignment film can be obtained.

The alignment film can be made into an alignment layer by applying an alignment layer-forming composition onto a transparent substrate and giving an alignment regulating force, for example. The composition for forming an alignment film can be appropriately selected and used from conventionally known materials such as photodimerization type materials.

Means for imparting an orientation regulating force to the alignment film can be known conventionally, and examples thereof include a rubbing method, a photoalignment method, and a shaping method.

The thickness of the alignment film is usually 1 to 1000 nm, preferably 60 to 300 nm.

<Polarizer (C)>

As the polarizer, you may use either an iodine polarizer, a dye polarizer using a dichroic dye, or a polyene polarizer. Iodine-based polarizer and dye-based polarizer can be generally manufactured using a polyvinyl alcohol-based film. The absorption axis of the polarizer corresponds to the stretching direction of the film. Accordingly, the polarizer stretched in the vertical direction (transport direction) has an absorption axis parallel to the longitudinal direction, and the polarizer stretched in the horizontal direction (transport direction and the vertical direction) has an absorption axis perpendicular to the longitudinal direction.

It is preferable to have protective layers on both sides of the polarizer.

As the protective layer, the same thing as exemplified as the transparent substrate of the retardation layer can be used. In addition, it is preferable that the protective layer has optical isotropy. In addition, the protective layer on the display element side of the polarizer may be replaced with a surface base material of the display element.

<Other floors, other members>

The display panel of the present invention may further include other layers and other members.

For example, each member of the display panel of FIGS. 1 and 2 may be bonded to each other via an adhesive layer. Further, the display panel may have functional layers such as a hard coat layer, an anti-glare layer, and an anti-reflection layer.

Further, the display panel of the present invention may have a touch panel between the display element (A) and the retardation layer (B). Examples of the touch panel include a resistive touch panel, a capacitive touch panel, an optical touch panel, an ultrasonic touch panel, and an electromagnetic induction touch panel. These touch panels may be provided with a pressure detection function.

[Display device]

The display device of the present invention is not particularly limited as long as it includes the display panel of the present invention, but it is preferable to include the display panel of the present invention, a drive control unit electrically connected to the display panel, and a housing to accommodate them. .

[Selection method of retardation layer of display panel]

The method for selecting a retardation layer of a display panel of the present invention includes a display element (A), a retardation layer (B) disposed on the light emission surface side of the display element, and a polarizer (C) disposed on the light emission surface side of the retardation layer. ), and the retardation layer (B) having a λ/4 retardation layer (B1), as the λ/4 retardation layer (B1), a λ/4 retardation layer that satisfies the following condition 1 is provided. It is to select.

<Condition 1>

The spectral reflectance of the display element is measured by the SCI method, and the average of the reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/4 retardation layer is -4.6002x+119.24 nm or more and -4.6002x+129.24 nm or less.

According to the method of sorting the retardation layer of a display panel of the present invention, it is possible to appropriately select a retardation layer whose color sense of the display panel is lowered, and thus product design of the display panel can be improved.

Further, in the method for selecting a retardation layer of a display panel of the present invention, the retardation layer (B) further has a λ/2 retardation layer (B2), and as the λ/2 retardation layer (B2), the following condition 2 is applied. It is preferable to select a satisfactory λ/2 retardation layer.

<Condition 2>

The spectral reflectance of the display element is measured by the SCI method, and the average of the reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/2 phase difference layer is -9.2004x+238.47nm or more and -9.2004x+258.47nm or less.

By selecting the retardation layer that satisfies the condition 2, it is possible to efficiently design a higher quality display panel.

Example

Next, the present invention will be described in more detail by examples, but the present invention is not limited at all by these examples. In addition, "part" and "%" are based on mass unless otherwise specified.

1. Reflectance of display elements A to C

Three types of commercially available organic EL display devices were prepared, and organic EL display elements were taken out of these organic EL display devices. Using the three organic EL display elements taken out as organic EL elements A to C, using a spectrophotometer (manufactured by Konica Minolta, brand name CM-2600d, measurement wavelength interval 10 nm), organic EL elements A to C The spectral reflectance of the SCI method was measured.

Considering that the absolute value of the change in reflectance per 1 nm within the measurement wavelength interval (10 nm) is equal, reflectance per 1 nm is calculated, and R ₁ /R ₂ and 400 to each of the organic EL elements A to C The average of the spectral reflectance of 700 nm was calculated. The calculated R ₁ /R ₂ is shown in Tables 1 to 3. Further, the reflectance of the organic EL elements A to C at every 1 nm is shown in FIG. 5. In addition, the graph of Fig. 5 is smoothed by Microsoft Excel (registered trademark) 2013.

2. Saturation of display panels A to C

On the organic EL elements A to C, the spectral reflectance of the SCI method of the organic EL display panels A to C obtained by arranging a λ/4 retardation layer, a λ/2 retardation layer, and a polarizing plate including a polarizer in this order in this order It measured using a color meter (manufactured by Konica Minolta Co., Ltd., brand name CM-2600d, measurement wavelength interval 10 nm), and "saturation" was calculated from the measured reflected light. As the λ/4 phase difference layer and the λ/2 phase difference layer, as shown in Tables 1 to 3, those having various phase difference values were used. As the polarizing plate, a general-purpose type polarizing plate containing an iodine polarizer (the polarizer protective film is a TAC film having optical isotropy) was used. In addition, the angle formed by the absorption axis of the polarizer and the alignment axis of the λ/4 phase difference layer was +75°, and the angle formed by the absorption axis of the polarizer and the alignment axis of the λ/2 phase difference layer was +15°.

An in-plane phase difference of the λ/4 phase difference layer as the x-axis and a smoothing-processed graph with the y-axis as saturation are depicted (Fig. 6), and the in-plane phase difference of the λ/4 phase difference layer at which the saturation is the minimum value was read. Was 118.35 nm, the organic EL display panel B was 119.45 nm, and the organic EL display panel C was 120.65 nm. In addition, the graph of Fig. 6 is smoothed by Microsoft Excel (registered trademark) 2013.

In addition, an in-plane phase difference of the λ/2 phase difference layer as the x-axis and a smoothing-processed graph with the saturation as the y-axis are depicted (not shown), and the in-plane phase difference of the λ/2 phase difference layer at which the saturation is the minimum value is read, and organic EL display Panel A was 236.7 nm, organic EL display panel B was 238.9 nm, and organic EL display panel C was 241.3 nm.

3. Calculation of criteria for condition 1 and condition 2

Fig. 7 shows an approximate straight line by the least squares method added to a scatter plot in which the in-plane retardation of the λ/4 phase difference layer is the y-axis when the saturation read from Fig. 6 is the minimum value and R ₁ /R ₂ is the x-axis. It is a drawing. From FIG. 7, it can be seen that R ₁ /R ₂ and the in-plane phase difference of the λ/4 phase difference layer representing the minimum saturation value of the display panel have a proportional relationship, and the proportional expression is R ₁ /R ₂ x , It can be represented by the following formula (1) by making the in-plane phase difference y.

In addition, Fig. 8 is a diagram in which an approximate straight line by the least squares method is added to a scatter plot in which R ₁ /R ₂ is the x-axis and the in-plane retardation of the λ/2 phase difference layer is the y-axis when the saturation becomes the minimum value. . From FIG. 8, it can be seen that R ₁ /R ₂ and the in-plane phase difference of the λ/2 phase difference layer representing the minimum saturation value of the display panel have a proportional relationship, and the proportional expression is R ₁ /R ₂ x , It can be represented by the following formula (2) by making the in-plane phase difference y.

4. Evaluation

Display panels A to C in which the display elements and retardation layers were combined as shown in Tables 1 to 3 were fabricated, and evaluated by visually seeing the color of the screen under illumination of a fluorescent lamp without lighting the panel. It was evaluated by the following criteria by 20 subjects.

A: 15 or more people answered that the color of the screen is good

B: 10 to 14 people who answered that the color of the screen is good

C: 9 or less people answered that the color of the screen was good

As shown in Tables 1 to 3, the display panels satisfying conditions 1 and 2 (Experimental Examples 1-7, 1-8, 2-7, 3-6 and 3-7) can suppress a decrease in color. You can confirm that there is.

10: display element
20: retardation layer
20a: λ/4 retardation layer
20b: λ/2 retardation layer
21: transparent substrate
22: alignment layer
23: adhesive layer
25: laminate having retardation layer
30: polarizer
100: display panel

Claims (7)

It has a display element (A), a retardation layer (B) disposed on the light emission surface side of the display element, and a polarizer (C) disposed on the light emission surface side of the retardation layer, and the retardation layer (B) is λ/ A display panel having 4 retardation layers (B1), and wherein the in-plane retardation of the λ/4 retardation layer (B1) satisfies Condition 1 below.
<Condition 1>
The spectral reflectance of the display element is measured by the SCI method, and the average of the reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/4 retardation layer is -4.6002x+119.24 nm or more and -4.6002x+129.24 nm or less. The method of claim 1,
The display panel, wherein the phase difference layer (B) further has a λ/2 phase difference layer (B2), and the in-plane retardation of the λ/2 phase difference layer (B2) satisfies Condition 2 below.
<Condition 2>
The spectral reflectance of the display element is measured by the SCI method, and the average of the reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/2 phase difference layer is -9.2004x+238.47nm or more and -9.2004x+258.47nm or less. The method according to claim 1 or 2,
The display panel, wherein the average of the spectral reflectance measured by the SCI method having a wavelength of 400 nm or more and 700 nm or less of the display element is 35% or more. The method according to any one of claims 1 to 3
The display panel, wherein the display element is an organic EL element or a micro LED element. A display device comprising the display panel according to any one of claims 1 to 4. It has a display element (A), a retardation layer (B) disposed on the light emission surface side of the display element, and a polarizer (C) disposed on the light emission surface side of the retardation layer, and the retardation layer (B) is λ/ In a display panel having four retardation layers (B1), as the lambda /4 retardation layer (B1), a lambda /4 retardation layer satisfying condition 1 below is selected as the lambda /4 retardation layer (B1).
<Condition 1>
The spectral reflectance of the display element is measured by the SCI method, and the average of the reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/4 retardation layer is -4.6002x+119.24 nm or more and -4.6002x+129.24 nm or less. The method of claim 6,
The retardation layer (B) further has a λ/2 retardation layer (B2) and, as the λ/2 retardation layer (B2), selects a λ/2 retardation layer that satisfies Condition 2 below. How to sort the layers.
<Condition 2>
The spectral reflectance of the display element is measured by the SCI method, and the average of reflectances of 400 nm or more and less than 550 nm is R ₁ , and the average of the reflectances of 550 nm or more and less than 700 nm is R ₂ , and R ₁ /R ₂ is calculated. do. When the value of R ₁ /R ₂ is x, the in-plane retardation of the λ/2 phase difference layer is -9.2004x+238.47nm or more and -9.2004x+258.47nm or less.

Images